The present invention relates to aerial image input/output apparatus and method for allowing an image of keys, a touch panel, or the like which is used for input/output operations of an information processing apparatus such as a computer or the like to appear as an aerial image in a blank space, and for inputting an instruction by operating the aerial image by a finger tip or the like. More particularly, the present invention relates to aerial image input/output apparatus and method for allowing an aerial image which is used for an inputting operation to appear in a space by using a key switch, a two-dimensional display, a line display, or the like which actually exists and for operating the aerial image.
In recent years, the multimedia in which information such as voice, image, and the like can be freely received and transmitted through a network has gloriously been advertised. Although the present time is called a multimedia age, it is an actual situation that in a conventional input/output device is used as a man-machine interface. In the conventional input/output device which is used as a man-machine interface, a CRT display, a liquid crystal display, or a plasma display is used to output and display. The displays are widely employed in the fields where their characteristics can be effectively used, respectively. For example, the liquid crystal display is used in small portable equipment, the plasma display is used in large equipment, and the CRT display is used in desktop information equipment, television, and the like. On the other hand, a keyboard, a mouse, a touch panel, and the like are used as input devices. Those devices are also widely employed in the fields where their characteristics can be effectively used. Further, as a device integrated with input/output functions, a touch panel switch device in which a touch panel is arranged on the surface of the CRT display is also widely used.
A general touch panel has a structure such that a plurality of transparent electrodes made of tin oxide or the like are arranged in both of the X direction (row direction) and the Y direction (column direction) and a position which is touched by a finger is specified by detecting an X coordinate and a Y coordinate of the position touched by the finger.
As a method of detecting the touch of the finger, there are the following methods: a method of detecting a change in electrostatic capacitance between the X and Y electrodes; a method of detecting a current change due to a short-circuit between the X and Y electrodes; a method of detecting human noises inducted in the X and Y electrodes; and the like. The touch panel is arranged on the surface of a display device such as a CRT display or the like and has a function to transmit an intention of a human to the information processing apparatus by touching a specific display position by a finger or the like. However, there is a limitation in a resolution of the present touch panel.
A display screen can be divided into tens or at most hundreds of portions, so that image information which requires a high resolution cannot be inputted. Since the touch panel switch device has a structure in which a touch panel and a display device which are separately manufactured are integratedly combined, a display surface and a touch surface are apart from each other by an amount corresponding to only by a thickness of glass or the like which protects the surface of the display, that is, by about a few mm. Consequently, a phenomenon in which the position of an image is deviated from the position to be touched by the finger occurs depending on an angle at which the image is seen. Such a phenomenon is also a factor to limit the resolution of the touch panel. Further, since two independent hardware devices having respective structures such as display device and input device are combined, the costs are inevitably high.
For such a conventional input/output device, there has been proposed a unique input method whereby when an image that is used for an inputting operation is allowed to appear as an aerial image in a space and the aerial image appearing in the space is touched by a finger, the position touched by the finger is detected, thereby inputting data (JP-A-6-348404). According to the input method, a display screen such as a CRT or the like is arranged on the lower surface of one end of a translucent plate and a real image of the display screen is projected at the corresponding symmetrical position on the upper surface of the translucent plate by two retroreflecting plates which are in contact with the other end of the translucent plate and each of which is arranged at an angle of almost 45.degree. from the translucent plate, thereby allowing an aerial image to appear. The retroreflecting plate is a reflecting plate to reflect an incident light in the incoming direction irrespective of an angle of incidence. When an object such as a finger or the like is inserted into the space in which the aerial image appears by the projection of the display screen, the position is detected by an object position detecting unit. A switch signal for inputting an instruction is generated on the basis of the detected position of the object and position information of a figure in the projected display screen. In the conventional input method in which the aerial image is displayed and the inputting operation is executed, the half of the light emitted from the image displayed on the display screen is reflected by the translucent plate and is reflected by the retroreflecting plate on the lower side and again enters the translucent plate. The further half of the light transmitted through the translucent plate forms an image at the corresponding position that is symmetrical to that on the display screen on the upper side of the translucent plate. On the other hand, as for the light emitted from the image of the display screen and transmitted through the translucent plate for the first time, the half of the light is reflected by the retroreflecting plate on the upper side. The half of the light is further reflected by the translucent plate and forms an image at the same position as that of the light reflected for the first time by the translucent plate. That is, according to the input method, even if the reflectance of the retroreflecting plate is equal to 100%, only the half of the light emitted from the display screen can be used in principle. In JP-A-6-348404, further, Scotchlites 7610 and 7615 manufactured by 3M Co., Ltd. are disclosed as retroreflecting plates. Although each of the retroreflecting plates is regarded as a most efficient retroreflecting plate which is presently available, it has been developed for a traffic-control sign or a signboard to reflect a headlight of a car. Therefore, the retroreflecting plate is not an optical member having an optically high precision, it is difficult to form a clear optical image in a space, and the reflectance is less than 50%. The aerial image obtained by the conventional input method is, consequently, very blurred and its brightness is also equal to or less than 1/4 of that of the display screen. The aerial image cannot help but is dark and indistinct. Thus, information which is outputted from an information processing apparatus or the like cannot be displayed at a resolution and a brightness which are similar to those of the CRT display, liquid crystal display, or the like. An apparatus for detecting the position of the finger or the like for the aerial image and inputting an instruction is separately formed and is used in combination with the display device of the aerial image. Such a construction is basically the same as the conventional touch panel and similar problems occur. A mirror arrangement for creating a real image in space of the object being displayed is disclosed in U.S. Pat. No. 3,647,284.